There is an affinity between refrigerants and the lubricants used in refrigeration compressors. As a result, the refrigerant circulating through the refrigeration system tends to contain some lubricant. The presence of lubricant interferes with heat transfer in the refrigeration system and the carry-over of lubricant may result in an inadequate amount of lubricant being available for lubricating the compressor. To minimize the carry-over of lubricant to the refrigeration system, the lubricant may be removed from the suction gas supplied to the pump structure or from the discharge gas before it passes into the heat exchange structure.